Narrative:

While doing the preflight walk around; I noticed some excessive hydraulic fluid under the aircraft. It appeared to be coming from a leaking hose on the forward right side of the wheel well compartment in between the a and B hydraulic tanks. I notified the captain and he called maintenance. We decided to board in hopes of a 'quick fix' to try and minimize our delay. The contract mechanic showed up; and after talking to maintenance control; told me he was going to be doing some tests. He went outside and I was sitting in my seat with the window open so we could communicate with each other while I turned hydraulic pumps on and off for him as he needed. While we were sitting there; the captain switched the power over to the APU the rampers disconnected the ground services. When I noticed the air was disconnected; I decided to turn the right pack on for the comfort of the passengers. Shortly after that I started to notice some smoke. My initial thought was that it was coming from the tug outside so I started to close my window. Then I realized it wasn't outside and I immediately turned the right pack off. While doing this I heard the flight attendants issue the evacuation command. I looked back and saw people running out the door. The whole incident lasted only a few seconds. The cabin filled with fumes very quick and the flight attendants did an excellent job of getting everyone out.

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Original NASA ASRS Text

Title: A B737-300 at the gate with passengers on board filled with fumes presumably from hydraulic over servicing. The flight attendants evacuated the cabin through the jet bridge.

Narrative: While doing the preflight walk around; I noticed some excessive hydraulic fluid under the aircraft. It appeared to be coming from a leaking hose on the forward right side of the wheel well compartment in between the A and B hydraulic tanks. I notified the Captain and he called maintenance. We decided to board in hopes of a 'quick fix' to try and minimize our delay. The Contract Mechanic showed up; and after talking to Maintenance Control; told me he was going to be doing some tests. He went outside and I was sitting in my seat with the window open so we could communicate with each other while I turned hydraulic pumps on and off for him as he needed. While we were sitting there; the Captain switched the power over to the APU the rampers disconnected the ground services. When I noticed the air was disconnected; I decided to turn the right pack on for the comfort of the passengers. Shortly after that I started to notice some smoke. My initial thought was that it was coming from the tug outside so I started to close my window. Then I realized it wasn't outside and I immediately turned the right pack off. While doing this I heard the flight attendants issue the evacuation command. I looked back and saw people running out the door. The whole incident lasted only a few seconds. The cabin filled with fumes very quick and the flight attendants did an excellent job of getting everyone out.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.